1. Field of the Invention
The present invention relates to an overlay operation method and an overlay control method, and more particularly, to an overlay operation method and an overlay control method to measure two patterns formed by a same process in combination with using a same photomask.
2. Description of the Prior Art
Semiconductor integrated circuits undergo a variety of processing steps during their manufacture, such as masking, resist coating, etching, and deposition. In many of these steps, material is overlaid or removed from the existing layer at specific locations in order to form the desired elements of the integrated circuit. Proper overlay of the various process layers is therefore critical. The shrinking dimensions of modern integrated circuits require more and more stringent overlay accuracy during the pattern transfer step. If the expected overlay tolerance is not met, the adverse result is a device that is defective or has reliability problems.
The measurement of the overlay between two or more successive layers on a wafer is one of the most critical process control techniques used in the manufacturing process of integrated circuits and devices. Overlay accuracy generally pertains to the determination of how accurately a first patterned layer aligns with respect to a second patterned layer disposed above or below it. Recently, overlay measurements are performed via test marks that are formed together with the layers of the wafer. The images of these test marks are captured via an imaging tool and an analysis algorithm is used to calculate the relative position between the marks from the captured images.
However, some issue still generated, for example, due to measurement deviation, the measured data of relative positions between the successive layers often fail to reflect their real positions. Also, since a position data of the previous marks in a previous region is used as a reference to manufacture the marks in present region, the position data of previous mark will affect the performance of presently formed mark. Thus, when the position data is deviated, the overlay accuracy between layers will decrease.
Therefore, there remains a need for controlling position data of overlay.